A tri-N-hydroxyamide-di-amide compound, identified by the name "Deferoxamine", is known to possess the following structural formula: ##STR3## existing as monohydrate crystals having a melting point of 138.degree.-140.degree. C. and a solubility in water at room temperature of about 1.2%. According to Merck's Index, 10th edition, this compound is obtained from Streptomyces pilosus or, alternately, is prepared from Ferrioxamine B which is an iron complex acting as a natural microbial growth factor isolated according to U.S. Pat. Nos. 3,118,823 and 3,153,621 with the general formula C.sub.25 H.sub.45 FeN.sub.6 O.sub.8. Deferoxamine has strong chelating properties for polyvalent metal ions, particularly for Fe(III) ions and less so for Fe(II) ions and is effective as an iron chelating agent for iron mobilization, and as an antidote for iron poisoning such as chronic iron poisoning caused by repeated blood transfusions in the treatment of Cooley's anemia.
It would be obviously desirable to have available a poly-N-hydroxamide having strong metal chelating properties comparable to those of Deferoxamine which can be prepared by a direct chemical reaction, as contrasted with isolation from complex natural materials, and particularly one that can be formed as a polymer in a variety of different structural shapes and with a broad range of physical properties, such as melting point, solvent solubility and the like. Similarly, a polyhydroxamide polymer has considerable potential for use as a chelating agent in the purification of water and other liquid media by the removal therefrom of heavy metal and alkaline earth metal ions.
It is, of course, well known to prepare nylon polyamide polymers by the condensation of an organic diamine with an organic diacid chloride and, inasmuch as the inventive polyhydroxamide polymers have a general analogy to nylon-type polyamides, a brief summary of the chemistry of nylon polymerization will be helpful to an understanding of the present invention.
Nylon, using the 6,6-polyamide as a convenient example, has the following structural formula: ##STR4## This polymer is formed by condensation polymerization and its precursors are hexamethylene diamine (H.sub.2 N--(CH.sub.2).sub.6 --NH.sub.2) and an adipoylhalide, such as adipoylchloride ##STR5## or adipoylester, such as methyl adipate ##STR6## The condensation polymerization scheme for adipoylchloride is ##STR7##